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Waveguide-type Optical Interferometer - Patent 8150219


The present invention relates to a waveguide-type optical circuit and more particularly to a polarization-independent waveguide-type optical interferometer having no polarization dependence.BACKGROUND ART As the optical communication technology moves forward, development of optical components capable of directly processing optical signals becomes increasingly important. Above all, a waveguide-type optical interferometer utilizing interference oflight in an optical waveguide structure integrated on a planar substrate is superior in mass production and has advantageous features such as low cost and high reliability. Typically included are an arrayed waveguide grating, a Mach-Zehnderinterferometer, and a lattice circuit, for example. Standard photolithography and etching as well as glass deposition technology such as FHD (flame hydrolysis deposition) are used as a basic method for fabrication of the waveguide-type optical interferometer. A procedure for the fabricationinvolves, first, depositing on a substrate an undercladding layer and a core layer with a higher refractive index than its surroundings, and then, forming a waveguide pattern on the core layer. The fabrication is accomplished by, further, burying thecore layer beneath an overcladding layer. Signal light propagates through the waveguide-type optical interferometer, as being confined within a waveguide formed by the buried core layer. FIG. 1 is a diagram showing the configuration of an asymmetric Mach-Zehnder interferometer (hereinafter called "asymmetric MZI") constructed of the waveguide-type optical interferometer. In the asymmetric MZI, an input waveguide formed of afirst input waveguide 101 and a second input waveguide 102 is connected to one end of an optical splitter 103. A long arm waveguide 107 and a short arm waveguide 108 of different lengths are connected to the other end of the optical splitter 103. Thelong arm waveguide 107 and the short arm waveguide 108 are connected to one end of a

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